As being the confining force will increase, the increase in resistance to longitudinal crack propagation leads to a gradual transition of shale failure method from longitudinal to inclined shear failure that reflects an escalation in rock plasticity. When the confining strain reaches 30 MPa, there are still nearby shear https://medium.com/@vertechs/revolutionizing-well-control-in-high-pressure-high-temperature-gas-drilling-environments-c212cb28aedd